The goals of our main project are to get a better understanding of the physiological regulation of the ornithine delta-aminotransferase (OAT) and its regulation in vivo. In humans, the mutation of OAT leads to the degeneration of the choroid and retina, causing a gyrate atrophy disease. There is no treatment for this human genetic disease; the only feasible approach would be to submit the patient to gene therapy via modified somatic cells lines. To accomplish this task, we are focusing on (1) the regulation of OAT gene in vivo and (2) the genetic modification of somatic cell lines mediated by recombinant retroviruses. With the idea of applying gene therapy, Moloney murine leukemia virus-based recombinant retrovirus vectors have been constructed. The human OAT cDNA was placed under the control of the enhancer-promoter regulatory elements derived from the Moloney murine leukemia virus long-terminal repeat. The construct was transfected into a safe packaging cell line, GP+E-86, to produce provirus particles. Supernatant from these ecotropic OAT producer cell lines was used to transduce mouse C57B1/6 embryonal fibroblasts and embryonic stem cells. We showed that the recombinant retrovirus transfers the OAT gene to the recipient cells, which produce an immunoreactive OAT. Northern blot analysis confirmed the presence of an OAT transcript in the transduced cell lines, even after a long period of time in vitro.